Machine for overwrapping multiple containers

ABSTRACT

A plurality of rigid containers or articles are grouped into a unit for overwrapping in thermoplastic, heat shrinkable film. The unit is inserted in a moving tube of the film which is subsequently rendered taut by directing streams of heated air on the film. As a result, the film tightens around the groups of articles and those portions of the tube at each end of the articles become constricted or necked down to retain the articles against longitudinal movement relative to the film tube. While still moving, each group of articles then encounters an orbiting hot wire for perpendicularly severing the tube at its constricted portion. After the severing of the tube, the overwrapped articles pass through a heat tunnel which further shrinks the film so that the film beomes tightly stretched and all portions thereof, including the severed free ends, closely conform to the overall shape of each group of articles.

United States Patent 1 1 Erlandson [451 Jan. 1,1974

[75] Inventor: Howard W. Erlandson, Green Bay,

Wis.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: Aug. 4, 1971 [2]] Appl. No.: 168,927

[52] U.S. Cl. 53/184, 83/326 [51] Int. Cl. B65b 53/02 [58] Field ofSearch 53/28, 30,48, 179,

Primary Examiner-Robert L. Spruill A!t0mey-F. W. Anderson et al.

[5 7] ABSTRACT A plurality of rigid containers or articles are groupedinto a unit for overwrapping in thermoplastic, heat shrinkable film. Theunit is inserted in a moving tube of the film which is subsequentlyrendered taut by directing streams of heated air on the film. As aresult, the film tightens around the groups of articles and thoseportions of the tube at each end of the articles become constricted ornecked down to retain the articles against longitudinal movementrelative to the film tube. While still moving, each group of articlesthen encounters an orbiting hot wire for perpendicularly severing thetube at its constricted portion. After the severing of the tube, theoverwrapped articles pass through a heat tunnel which further shrinksthe film so that the film beomes tightly stretched and all portionsthereof, including the severed free ends, closely conform to the overallshape of each group of articles.

4 Claims, 7 Drawing Figures PATENTEU 3. 782,070

sum 1 or 4 INVENTOR. HOWARD W. ERLANDSON BY [0. v M

ATTORNEYS PATENTED 3.782.070

SBEEI 3 BF 4 MACHINE FOR OVERWRAPPING MULTIPLE CONTAINERS BACKGROUND OFTHE INVENTION Food and beverages, usually packaged in bottles or cans,are often merchandized in groups containing two or more items in acardboard carrier which confines the items so that they maintain aselected arrangement. The carriers are usually formed with cutouts andtabs or lugs to maintain the arranged order of the items, and areprinted to identify and create appeal for the product. Thus, carriers ofthis type require printing of the rolled parent cardboard stock, diecutting and creasing, and packaging for shipment to bottling or canningfacilities. Further, the carriers conceal most of the contents, requiresetup machinery, and often need another machine to thereafter close andadhesively seal the carriers.

There are other varieties of carriers designed with the object ofmaintaining the cans or bottles in an assembled group by engaging thetops of the articles by a sheet of thermoformed, semi-rigid plastic. Theobvious advantage of this type of carrier is that it protects theopening end of the containers, is inexpensive to make, and themerchandising data, artwork and trademark on each individual item isvisible, therefore obviating the need of printing the carrier itself.Other types of carriers consist of a sheet of semirigid plastic with aseries of punched holes which is forcibly fitted onto the sides of theupper ends of the containers. These and similar types of carriers havethe distinct disadvantage that the bottoms of the containers are looseand free to move, thus increasing the risks of breakage or damage.

SUMMARY OF THE INVENTION lnterspaced groups of articles, such as cans,are continuously conveyed with a heat-shrinkable transparent film webthrough a web former andover a longitudinal seam sealer to form the webinto a continuous tube around the articles. Heaters, which force heatedair blasts against the sides, top and bottom of the tube downstream ofthe web former and the seam sealer, then effect a preshrinking of thetube so that it is necked down or constricted between groups of thearticles in order to lock the articles in place and to make the web tubetaut for a hot wire cutoff operation between the article groups.

By providing structure for moving the hot wire cutoff or severingmechanism in a diagonal path normal to the direction of movement of theentubed articles, there is no relative motion between the severingmechanism and tube, whereby the severing mechanism descends in avertical path relative to the tube. Accordingly, the length of the tubebetween groups of articles is very short so that no waste or excess webresults, even though the overwrap operation is carried out with thearticles moving with continuous straight-line motion at a relativelyhigh constant. velocity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic sideelevation of the wrapping machine of the present invention.

FIG. 2 is an exploded diagrammatic isometric view of the majorcomponents of the FIG. 1 wrapping machine.

FIG. 3 is a diagrammatic isometric view, generally similar to FIG. 2,but including the operatingfunctions performed in producing a packageunit comprising a group of articles enveloped in a heat-shrunk plasticweb.

FIG. 4 is an enlarged diagrammatic transverse section.

FIGS. 5-7 are diagrammatic operational views illustrating successivestages of operation of a hot wire cutoff mechanism for severing thetubular web between adjacent groups of articles.

DESCRIPTION OF THE PREFERRED EMBODIMENT The wrapping machine 10 (FIG. 1)of the present invention includes a floor-supported frame structure 12and operates as briefly outlined below. The basic machine is a knowntype of wrapping machine, other variations of which may be found in U.S.Pat. Nos. 2,682,331, 2,762,178 and 3,009,298 wherein each machine ismodified for a particular purpose. In the present invention, thewrapping machine 10 is provided with an input or receiving conveyor 14having two laterally aligned lanes of pusher lugs 16. Each lug propelsthree containers C which with the laterally adjacent containers comprisethe contents of a multipack M.

A web W from an overhead roll R of thermoplastic, heat-shrinkable webmaterial is drawn through a web former F wherein the edge portions ofthe web are curled downward over the two adjacent lanes of containers toform a tube T with the edges in overlapping relation along thecenterline at the bottom of the tube. Immediately downstream of the webformer F, at a sealing station 18, the overlapping edges are bondedtogether by a sealing bar 20 (FIG. 3), and the entubed containers aredeposited in timed relation upon a continuously moving main conveyor 22.The tube T now envelops and is sealed around the spaced containergroups, and the weight of the containers prevents relative longitudinalmotion between the tube, the conveyor and the container groups. Itshould be noted that an overlapping seal is not an essentialrequirement; the tube may also be formed with downturned lower edgesforming abutting flanges sealed together in the conventional mannerknown in the art as a fin seal.

Adjacent heaters H direct continuous blasts of heated air against eachside of the tube T to effect a preliminary shrinking of the web and drawthe web taut. Thus, the tube T is caused to tightly grip the containers,and in the open space between groups of containers the tube becomesconstricted or necked-down, and taut. The heaters are commerciallyavailable, electrically energized units, and each includes a heatcontrol, not shown, plus a centrifugal blower and a drive motor.

Near the downstream heaters H, the entubed containers pass under acutoff or severing mechanism S which severs the moving tube T along avertical plane precisely at mid point between the container groups. Thecutoff mechanism S comprises a particularly important feature of thepresent invention, as later described, because it allows continuous,relatively high speed movement of the web tube T while severing the tubeperpendicularly relative to its length to form the individual multipacksM.

At the discharge end of the main conveyor 22, the multipacks M may bedeposited upon another conveyor, a gravity chute, or hand conveyed to aheating tunnel 24. The heating tunnel is a commercially available unithaving built-in conveying means for moving the multipacks through acontrollably heated environment and effecting the final shrinking of thefilm wrapper covering each multipack. After traversing the heatingtunnel, the wrapper is tightly shrunk over the containers, and thesevered ends of the wrapper lie completely flat, with the apertureswhich were formerly the open ends of the tube now much smaller than theends of the multipacks. Thus, each multipack M when wrapped in the abovedescribed manner, has a tightly shrunk transparent wrapper which revealsthe contents, holds the contents in rigid alignment, and in all respectsmakes each multipack M a unitary package which can be formed at highproduction speeds and at low cost.

With more specific reference to the wrapping machine 10, FIG. 2illustrates the major drive components, power for which is provided by amotor M,,. A V belt and pulley drive unit 26 couples the motor to ashaft 28 which, through meshed gears 30, powers a main drive shaft 32.Bevel gears at 34 on one end of the drive shaft 32 power an auxiliarydriveshaft 36 that is connected, by means not shown, to the inputconveyor 14 for driving the conveyor and the pusher lugs 16 in timedrelation to the other operating components of the wrapping machine.

The main drive shaft 32 is also provided with a chain and sprocket driveconnection 38 to a planetary transmission 40 having a control shaft 42and a hand crank control 44 for adjusting the timing of the hot wiresevering mechanism to proper position in relation to midpoint betweencontainer groups. This can be adjusted while machine is running. A drivetrain 46 powers a knock out clutch 48 which in the event of amalfunction in the machine will uncouple the driving power from a pairof clutch shafts 50 and 52, and also stop the motor M by means of aclutch switch, not shown. For driving the overhead tube severingmechanism S, the clutch shafts 50 and 52 are provided with chain andsprocket drive connections 54 and 56, respectively, which rotate coaxialdrive sprockets 58 and 60 of the severing mechanism S. Each of thelatter drive sprockets is associated with two idler sprockets 62, and atriangular chain loop 64 or 66. A fixed mounting plate 68 (FIG. 4)carries each group of sprockets.

For severing the tube T between groups of articles entubed therein, thesevering mechanism S includes a hot wire cutoff or severing element 70(FIG. 2) and a tie bar 72 that extends between the chain loops 64 and 66for movement in a triangular path. The severing element is formed of atensioned, electrically energized nichrome wire, the mounting for whichis later described. Because the cutoff unit is continuously orbited byits supporting chain loops, the electrical connecting wires 74 (FIGS. 2and 4) to each end of the wire 70 are rotated to prevent their beingtwisted. For this purpose, the wires 74 are respectively connected toslip rings 76 and 78 that are rotated by chain and sprocket driveconnections 80 and 82 from the clutch shafts 50 and 52. The slip ringsare engaged by conventional brushes, not shown, for conductingelectrical energy to the wire 70.

The main conveyor 22 includes two side by side pairs of conveying chains84 and 86 trained over drive sprockets 88 on a conveyor driveshaft 90.Power for the shaft 90 is provided from the clutch shaft 52 by a drivetrain 91 which includes meshed reversing gears at 92 to obtain theproper rotation. In order to clear the main driveshaft 32, the lowerflights of the chains 84 and 86 are trained under freely rotatable idlersprockets 94 on the main driveshaft.

The air blast from the lowermost heater H (FIG. 3) must impinge thebottom of the tube T for proper operation during heat-shrinking of thetube. To provide a minimally obstructed heat path, the support surfacefor the entubed containers comprises two laterally spaced flights ofsupport slats 96, and no slats are used between the container groups.For complete severance of the film tube T, the wire of the tube severingmechanism S must, of course, pass below the bottom plane of the tube.Thus, omitting the conveyor support slats 96 between groups ofcontainers also provides clearance space for the wire.

F IG. 3 covers substantially the same area of the wrapping machine asFIG. 2, except that the web former F is included because the componentsare not in exploded relation. With reference to FIGS. 3 and 4, the tubesevering mechanism S includes two L-shaped brackets 98 secured to thechain loops 64 and 66, and interconnected by the tie bar 72. Theelectrically heated nichrome wire 70 for severing the tube T is carriedby the brackets 98. Thus, each bracket is provided with a recessmounting a cup-shaped insulator 104 coaxial with a clearance hole in thebracket.

The ends of the wire 70 extend through each clearance hole, through acompression spring mounted in the recess, and are fixed to washers whichslightly compress the springs to tension the wire 70 and maintain itstraight and taut, regardless of thermal expansion. Each of theelectrical conductors 74 is bonded to the wire 70 and extends through aninsulator sleeve 108 to an electrical plug 110. Receptacles 112 for theplugs are respectively rotated by the drive connections and 82 once foreach orbit of the wire 70 to prevent twisting off the electricalconductors 74.

When the motor M (FIG. 2) is energized and the wrapping machine 10 isplaced in operation, the groups of containers C are continuouslyconveyed at a linear velocity corresponding to a production rate of tomultipacks M per minute. At the present time, the production speed islimited to this approximate rate by the available heat shrinkablewrapping films, not by the disclosed structural components of thepresent invention. Thus, it is a particular feature of the presentinvention that the severing mechanism S is capable of effecting verticalseverance of the tube T at production rates exceeding those presentlyachieved, as improved wrapping films become available.

The severing mechanism S (FIGS. 5-7) advances the heated nichrome wire70 in a path diagonally downward across the tube T, and at a velocitysuch that the tube T (FIG. 5) is severed along a vertical reference lineR exactly midway between adjacent groups of containers C. In the presentembodiment, the stated result is effected as follows:

Each group of the container support slats 96 have an aggregate lengthalong the conveying path of 12 inches, and four slats are omittedbetween groups of slats. Thus, the center to center spacing of thegroups of containers is 12 inches and the pusher lugs 16 (FIG. 1) on theinlet conveyor 14 are spaced 12 inches apart and timed to longitudinallycenter each group of containers relative to its support slats. It shouldbe noted that it is permissible for the container groups to slightlyoverhang the support slats or lie slightly within the edges of thetrailing and leading slats, thus enabling the severing mechanism S tohandle a range of different diameter containers, as well as taller orshorter containers, without any structural changes.

The chain loops 64 and 66 of the severing mechanism S form equilateraltriangles wherein a pitch line 114 (FIG. 5) of the descending flight ofthe chain loop 66, in conjunction with an imaginary vertical line 116,and a horizontal line 118 coincident with the support surfaces of theconveyor slats 96, define a 30-60-90 triangle. Thus, the pitch line 114is twice the length of the base line 118, and the linear velocity of thechain loops 64 and 66 is about 2.23 times faster than the velocity ofthe main conveyor chains 84 and 86. With this arrangement, once theinitial timing of the chain loops has been set so that the wire 70 firstcontacts the tube T at the reference line R, the horizontal component ofmovement of the wire 70 exactly matches the movement of the tube T, andthe heated wire severs the moving tube along the reference line R, andexactly between all succeeding groups of containers.

In order to index the wire 70 with each open gap in the tube T, thelength of each chain loop 64 and 66 (using only one hot wire) must betwice the distance between severing operations, or twenty four inches.It is believed evident that more than one severing wire can be used insome installations, that the disclosed velocities, geometry and driveratios are merely exemplary, and that similar structural arrangementscan be employed to assure vertical movement of the wire 70 relative tothe tube T.

After severing the tube T (FIG. 6), the wire 70 passes below theconveying surface through the gap between the conveyor slats 96, andthen travels an ascending flight 120. Since the geometry of the flight120 relative to the conveying surface is the reverse of the flight 114,the wire 70 retains its centered relation between the moving containergroups and exits without further contact with the tube T for the nextsevering operation in centered relation between the trailing containersof one container group, and the leading containers of the succeedingcontainer group.

Residual heat and the tension in the severed tube T (FIG. 6) causes thefilm to draw toward the ends of the container groups as it is severed sothat upon the completion of the severing operation, as shown in FIG. 7,the apertured ends of the tube at 121 lie relatively flat and theapertures 122 are small in relation to the area covered by the adjacentweb material to firmly lock the containers C in place. In order tocomplete the shrinking of the tube so that all sides thereof arecompletely taut and conform very close to the shape of the contents,each multipack M is fed into the heat tunnel 24 (FIG. 3) and istransported therethrough by conveying chains 124 for heat treatmentcompatible with the specific film being used and insufficient to damagethe product in the containers.

Each multipack M formed as outlined above has several advantages overthe previously mentioned prior art packages. An important advantage isthat no external printing is required when transparent films are used,because the containers are clearly visible. Further, the wrappingaffords complete protection for the tops of the containers so that themultipacks can be subjected to all of the usualand numerous handlingprocedures before reaching the consumers table, and yet the containerswill be substantially as clean as when they left the production line.The cost advantage is significant,

due to the high production rates attainable with the continuous motionmode of operation, the simplicity of the overall machine, the relativelylow cost of heat shrinkable web materials, and the elimination ofexternal printing to identify the contents. In regard to high productionrates, it is evident that the structure which enables continuousstraight line motion of the multipacks, namely, the severing element Swhich includes the orbiting hot wire 70, forms a basic and highlyimportant aspect of the present invention.

The two-stage heat shrinking operation is also important because thetube T is constricted between groups of containers immediately after thetube is formed and sealed, thus locking the containers in place andmaintaining the spacing of the container groups for the tube severingoperation. Because of the operating mode of the severing mechanism S,continuous conveying movement for high speed production output isattained in a relatively simple and durable machine which is readilyadaptable to handle different sizes and types of containers formultipack wrapping.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and var iation may be made without departing from what isregarded to be the subject matter of the invention.

What is claimed is:

l. A multipack overwrapping machine comprising means for conveying agroup of articles along a predetermined path, means for entubing themoving group of articles in a heat shrinkable film web, means fordirecting a hot air blast against the tube for effecting partialshrinkage and constriction of the tube at opposed ends of the group ofarticles to lock the articles in place within the tube, means forsevering the constricted portions of the moving tube to provide anindividual multipack, and means for heating each multipack to completethe shrinkage of the tube so that the tube conforms closely to the shapeof the articles therein, said severing means including an endlessflexible loop element at each side of said conveying means, each of saidloop elements including a declining linear flight extending downwardacross and beyond said conveying path and an inclining linear flightextending upward across said conveying path, a resistance heating wirecarried by said loop elements, and means for concurrently driving saidloop elements at a velocity producing a forward component of movement,for each of said flights, that causes said resistance wire to remain invertical alignment with a predetermined moving point on said conveyingmeans.

2. Apparatus according to claim 1 and electrical junction meanssubstantially in the plane of each of said loop elements andsubstantially equidistant from the orbital path followed by the adjacentend of said resistance wire, an electrical conductor connected betweeneach of said junction means and said resistance wire, and means forrotating both of said junction means once per orbit of said resistancewire.

3. Apparatus according to claim 2 and a slip ring rotatable with each ofsaid junction means and electrically connected thereto for conductingelectrical energy to said resistance wire.

4. Apparatus according to claim 3 and resilient mounting means for saidresistance wire intermediate each end portion of said wire and saidflexible loop elements to tension the wire and maintain it linearregardless of thermal expansion.

1. A multipack overwrapping machine comprising means for conveying agroup of articles along a predetermined path, means for entubing themoving group of articles in a heat shrinkable film web, means fordirecting a hot air blast against the tube for effecting partialshrinkage and constriction of the tube at opposed ends of the group ofarticles to lock the articles in place within the tube, means forsevering the constricted portions of the moving tube to provide anindividual multipack, and means for heating each multipack to completethe shrinkage of the tube so that the tube conforms closely to the shapeof the articles therein, said severing means including an endlessflexible loop element at each side of said conveying means, each of saidloop elements including a declining linear flight extending downwardacross and beyond said conveying path and an inclining linear flightextending upward across said conveying path, a resistance heating wirecarried by said loop elements, and means for concurrently driving saidloop elements at a velocity producing a forward component of movement,for each of said flights, that causes said resistance wire to remain invertical alignment with a predetermined moving point on said conveyingmeans.
 2. Apparatus according to claim 1 and electrical junction meanssubstantially in the plane of each of said loop elements andsubstantially equidistant from the orbital path followed by the adjacentend of said resistance wire, an electrical conductor connected betweeneach of said junction means and said resistance wire, and means forrotating both of said junction means once per orbit of said resistancewire.
 3. Apparatus according to claim 2 and a slip ring rotatable witheach of said junction means and electrically connected thereto forconducting electrical energy to said resistance wire.
 4. Apparatusaccording to claim 3 and resilient mounting means for said resistancewire intermediate each end portion of said wire and said flexible loopelements to tension the wire and maintain it linear regardless ofthermal expansion.